This invention relates to medical devices having an engaging assembly for engaging material in a body. More particularly, the invention relates to retrieval assemblies, such as baskets, graspers, forceps, or screens for holding material, such as a stone, in a body tract for treatment of the material by a lithotriptor, e.g., a laser lithotriptor.
Medical retrieval devices generally are used to retrieve material, such as a stone, from a body tract or to stabilize material in a body tract for fragmentation by a lithotriptor, such as a laser lithotriptor. In existing medical retrieval devices, the retrieval assembly, such as a basket, is formed from a plurality of wire legs or loops, or by a fabric, such as a metallic fabric or mesh. The retrieval assembly is used to capture material such as a ureteral, urethral, renal, biliary or gallbladder stone. Once the stone is captured in the basket, an attempt is made to remove the stone by withdrawing the medical retrieval device from the body while the stone is captured in the retrieval assembly.
In some clinical situations, a stone located within a body tract is too large or too jagged to be withdrawn from the body tract while captured in the retrieval assembly of a medical retrieval device. Under these conditions, the stone must be fragmented into smaller particles.
When stones are fragmented within a body tract by a lithotriptor, the stone must first be stabilized. Typically, a medical retrieval device is used to capture a stone in the retrieval assembly. With the stone held in position within the retrieval assembly, a lithotriptor, such as a laser lithotriptor, comes into proximity with the stone and the stone is fragmented bathe lithotriptor. After the stone is fragmented, the stone fragments can be removed by the same or a different medical retrieval device, or the fragments can be left in the body to be eliminated naturally.
Laser lithotriptors have gained increasingly wide application in the treatment of stones that are lodged within a body tract. Several lasers, such as the Nd: YAG laser and the holmium: YAG laser, have become available for medical applications.
In general, the invention relates to a medical retrieval device comprising a handle, a sheath having a lumen, and a laser-resistant engaging assembly for retrieving material from a body. At least a portion of the laser-resistant engaging assembly includes at least one substance that is resistant to damage induced by laser energy. The laser-resistant substance can be incorporated within the engaging assembly itself or coated on the engaging assembly. The laser-resistant substance can be a fluorocarbon plastic such as expanded polytetrafluoroethylene (EPTFE), polytetrafluoroethylene (PTFE), tetrafluoroethylene (TFE), fluorinated ethylenepropylene (FEP), perfluoroalkoy (PFA), ethylene tetra-fluoroethylene (ETFE), polyvinylidene fluoride (PVDF). The laser resistant material can also be ceramics or gold, silver or nickel plating polished to a reflective surface, or any material (or combination of materials) that is resistant to damage induced by laser energy released from medical lasers, such as, medical Nd:YAG or holmium:YAG lasers.
Medical retrieval devices having engaging assemblies that are resistant to laser energy in accordance with the invention have advantages over conventional medical retrieval devices when the inventive devices are used in combination with laser energy therapy. For example, laser lithotriptors are effective in fragmenting stones that are captured in a retrieval assembly of a medical retrieval device. One drawback of the combined use of a laser lithotriptor and retrieval assembly is the susceptibility of the retrieval assembly, or parts of the retrieval assembly, to laser energy-induced damage. Damage may be caused by misfiring, misdirection or unavoidable misalignment of the laser lithotriptor-with the stone. Laser energy-induced retrieval assembly damage may cause components of the retrieval assembly, such as the legs, to become roughened or broken. Broken or roughened legs expose sharp ends or surfaces that can traumatize the body tract.
An advantage of a medical retrieval device according to the invention is that its engaging assembly is resistant to damage from incident laser energy. Any damage to the engaging assembly caused by laser energy could potentially traumatize the body tract into which the medical device is placed. By including laser-resistant materials in at least a portion of the engaging assembly, the risk of trauma to a body tract that could be induced by a damaged engaging assembly is reduced or eliminated.
In one aspect, the invention features a medical retrieval device comprising a handle, a sheath having a lumen, and a laser-resistant engaging assembly for engaging material in a body. The laser-resistant engaging assembly includes a substance resistant to damage induced by laser energy. The laser-resistant substance is incorporated into at least a portion of the components of the engaging assembly or applied to at least a portion of the surface of the engaging assembly. The laser-resistant engaging assembly has a position in which the laser-resistant engaging assembly is enclosed within the lumen of the sheath (a closed position) and another position in which the laser-resistant engaging assembly extends from the distal end of the sheath and out of the sheath lumen (an open position). The laser-resistant engaging assembly can transition between the closed position and the open position by axial movement of the sheath over the engaging assembly, or the engaging assembly can move axially as the sheath stays fixed. In general, there can be relative movement between the sheath and the engaging assembly to place the engaging assembly in the closed position, the open position, or any position between the closed and open positions.
An embodiment in accordance with this aspect of the invention can include an elongated member that extends axially in the sheath lumen, is operably attached at its distal end to the laser-resistant engaging assembly, and is joined at its proximal end to an actuator in the handle. In this embodiment, the laser-resistant engaging assembly is moved when the elongated member is moved by the actuator in the handle.
Other embodiments in accordance with this aspect of the invention can include a laser-resistant engaging assembly such as a surgical retrieval basket comprising a plurality of legs, or, alternatively, a plurality of loops. The laser-resistant engaging assembly can also have a single loop configuration. In some embodiments, the laser-resistant medical retrieval basket has a tipless, or atraumatic tip, at the distal end of the basket. In still other embodiments, the laser-resistant basket can have at least one individually-actuateable leg, or a D-shaped, V-shaped or rectangular leg. The inside surface or the outside surface of at least one leg can be treated with at least one laser-resistant substance.
In another embodiment, the laser-resistant engaging assembly has a proximal portion and a distal portion. A distal portion of the laser-resistant engaging assembly can be used for capturing material in a body when the distal portion is extended beyond the distal end of the sheath and a proximal portion of the assembly is collapsed within the sheath. With this embodiment of the laser-resistant engaging assembly, the captured material can be released from the engaging assembly when the distal and proximal portions of the engaging assembly extend beyond the distal end of the sheath.
In yet another embodiment of the invention, the laser-resistant engaging assembly includes a grasper having a plurality of opposing loops, such as two loops, the loops being attached at the base of the engaging assembly and unattached to one another at their distal ends. The loops of the laser-resistant retrieval assembly have a collapsed position in which the loops are collapsed within the lumen of the sheath, and another position in which at least a portion of the loops extend from the distal end of the sheath and out of the lumen. The loops are moveable between an open and a closed position with the distal ends of the loops being closer together in the closed position than when in the open position to allow capture and release of material.
In another aspect, the invention involves a method for treating material in a body. The method includes the steps of inserting a medical retrieval device into a body having a proximal handle, a sheath having a lumen and an engaging assembly. The engaging assembly has at least a position in which the engaging assembly is within the lumen of the sheath and another position in which the engaging assembly extends from a distal end of the sheath and out of the sheath lumen. At least a portion of the engaging assembly includes a substance resistant to damage from laser energy. The material in the body is held by the engaging assembly and is treated by the laser. The medical device is removed from the body.